Inflators are supplying, for instance, gas for inflating an airbag or for driving a belt tensioner. It is important in all cases that the generated gas is quickly made available. According to a known technology, the propellant is generated at least partially from a pressurized gas stored in the housing of the inflator. The housing is opened by a pyrotechnic igniter destroying a membrane enclosing the housing to the outside so that the gas can flow out.